gpio: use (!foo) instead of (foo == NULL)

Signed-off-by: Varka Bhadram <varkab@cdac.in>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpio-da9055.c b/drivers/gpio/gpio-da9055.c
index b8d7570..7227e6e 100644
--- a/drivers/gpio/gpio-da9055.c
+++ b/drivers/gpio/gpio-da9055.c
@@ -146,7 +146,7 @@
 	int ret;
 
 	gpio = devm_kzalloc(&pdev->dev, sizeof(*gpio), GFP_KERNEL);
-	if (gpio == NULL)
+	if (!gpio)
 		return -ENOMEM;
 
 	gpio->da9055 = dev_get_drvdata(pdev->dev.parent);